Field of the Invention
The present invention relates to a technique of performing printing based on image data by scanning a printhead including a plurality of printing elements.
Description of the Related Art
In a printing apparatus disclosed in Japanese Patent Laid-Open No. 2007-118595, raster data is stored in a DRAM called a print buffer and having a burst readout function, and, when a predetermined amount is stored, the stored data is read out and transferred to a printhead after horizontal to vertical (HV) conversion. HV conversion is conversion which rearranges raster data in which pixels are sequentially arranged in the line direction, into data in which the pixels are arranged in accordance with the arrangement of printing elements of a printhead.
On the other hand, it is also possible to perform HV conversion before data is stored in the print buffer, and read out column data. In this case, however, there is the possibility that a predetermined size to be read out by burst readout and a data amount necessary to perform registration adjustment do not match each other. Note that “registration adjustment” is the adjustment of a printing position on a medium, particularly, the adjustment of a printing position in the conveyance direction. In this arrangement, it is necessary to prolong the burst length for data readout, and perform a bit shift operation for cutting out a necessary bit from readout data, that is, the circuit is complicated.
On the other hand, a printing method called column thinning is disclosed in a printing apparatus disclosed in Japanese Patent Laid-Open No. 2013-154590. Column thinning is a printing method of performing a printing operation on only pixel columns (columns) periodically selected from columns arranged in the main scanning direction of a printhead. When column thinning is performed, therefore, a discharge operation is performed in each printing scan at a pixel density lower than the density of actually arranged pixels. Since this can decrease the apparent driving frequency of each individual printing element, it is possible to increase the scanning velocity of a carriage, and increase the printing speed.
Unfortunately, if printing is performed by the column-thinning print mode as described in Japanese Patent Laid-Open No. 2013-154590 when raster data (raster image data) is stored in the print buffer as described in Japanese Patent Laid-Open 2007-118595, data which is read out and discarded is generated with respect to readout raster data. This decreases the effective data readout band in readout from the print buffer. This decrease in effective data readout band may make the printing speed difficult to increase.